Author Topic: Is PCI card based hosted SCSI RAID a thing for MacOS?  (Read 3223 times)

Offline aroneox

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Is PCI card based hosted SCSI RAID a thing for MacOS?
« on: November 22, 2022, 11:55:51 AM »

I would like to put a striped RAID 0 SCSI array into my PowerMac G4 Gigabyte. I would like to have it recognized and bootable into both MacOS 9 and OS X. Is this something that can be done on the Mac?

Not sure if hardware hosted SCSI RAID is a thing on a Mac. I know from my limited experience in the Windows/Linux world, the PCI card would handle the hosting with its own accessible BIOS settings and then Windows sees it as a single drive.

I currently have an ATTO ExpressPCI PSC PCI SCSI card w/ internal 68-pin and 50-pin headers, and an external 68-pin(?) connector. And I want to connect two 18gb Quantum Atlas 10,000 RPM server drives in a RAID 0 (striped) configuration. I would use this drive-array to boot into MacOS 9.2 and OS X 10.4 Tiger. The RAID array serves no other purpose than for me to feel cool when the jet-engine decibel SCSI drives spin-up and perform their ADHD accessing. This is a for a retro-computing nostalgia project. It doesn't serve any critical functions or need to have server level performance.

My SCSI knowledge ends around the PowerPC 603/604 era. Please educate me if you've got SCSI knowledge.

Offline aroneox

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #1 on: November 22, 2022, 12:08:23 PM »
This is my current SCSI card and HD -- The ATTO ExpressPCI PSC SCSI PCI card, and Quantum Atlas SCSI:


Offline ivanshpak

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #2 on: November 24, 2022, 03:11:38 AM »

I would like to put a striped RAID 0 SCSI array into my PowerMac G4 Gigabyte. I would like to have it recognized and bootable into both MacOS 9 and OS X. Is this something that can be done on the Mac?

Not sure if hardware hosted SCSI RAID is a thing on a Mac. I know from my limited experience in the Windows/Linux world, the PCI card would handle the hosting with its own accessible BIOS settings and then Windows sees it as a single drive.

I currently have an ATTO ExpressPCI PSC PCI SCSI card w/ internal 68-pin and 50-pin headers, and an external 68-pin(?) connector. And I want to connect two 18gb Quantum Atlas 10,000 RPM server drives in a RAID 0 (striped) configuration. I would use this drive-array to boot into MacOS 9.2 and OS X 10.4 Tiger. The RAID array serves no other purpose than for me to feel cool when the jet-engine decibel SCSI drives spin-up and perform their ADHD accessing. This is a for a retro-computing nostalgia project. It doesn't serve any critical functions or need to have server level performance.

My SCSI knowledge ends around the PowerPC 603/604 era. Please educate me if you've got SCSI knowledge.

There are absolutely no problems with SCSI on OS9, although your adapter is not very suitable for the full impact of this technology, you need a ATTO UL3D card and also if you want to create a raid array you can do it from OS-X using the Atto utility and extensions for detecting raid arrays "OS9 enabler"


Offline ivanshpak

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #3 on: November 24, 2022, 03:20:24 AM »
In the photo, two machine, one (MDD FW800) is BOOT in OS-X with 4 SCSI HDD 15k RAID 0 (Apple raid) ATTO UL4D

Another machine (MDD 2003) for music production has an internal two HDD 15k RAID 0 (ATTO Express Raid) ATTO UL3D


Who is well versed in the topic knows that the SCSI controller should be in the last PCI slot, when I took a photo, I did experiments with the system boot speed in different slots, and stability

Offline aroneox

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #4 on: November 24, 2022, 10:01:15 AM »
Appreciate the reply. Very nice setups!

To clarify, can my ATTO ExpressPCI PSC pictured do a RAID setup?

And if it does happen to be YES it can do RAID, would it be bootable from that card into both OS 9 and OS X 10.4 Tiger?

I am unsure how SCSI implements its RAID configurations. Looking over your setups, the 4x RAID looks like it just runs on a single SCSI cable. But the 2x RAID, I see two separate cables. It is my understanding that while SCSI RAID can run multiple drives off a single cable (single-channel), only one drive can talk at a time. With a two separate cables on a dual-channel, assuming a 2x drive RAID setup, then each of the drives potentially has full saturation available from the controller (discounting other limitations such as bus speed, etc.). Correct?

Does my G4 Gigabit, with it 33mhz PCI bus, even have a chance of needing a dual-channel setup considering that low bus speed?

Considering that, would it benefit from the UL3D card (let alone a ULD4)?

And looking over eBay, UL3D cards look to be PCI-X. Can PCI-X cards be used in my G4 Gigabit with basic, boring PCI slots?

Offline ivanshpak

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #5 on: November 24, 2022, 10:46:52 AM »
Appreciate the reply. Very nice setups!

To clarify, can my ATTO ExpressPCI PSC pictured do a RAID setup?

And if it does happen to be YES it can do RAID, would it be bootable from that card into both OS 9 and OS X 10.4 Tiger?

I am unsure how SCSI implements its RAID configurations. Looking over your setups, the 4x RAID looks like it just runs on a single SCSI cable. But the 2x RAID, I see two separate cables. It is my understanding that while SCSI RAID can run multiple drives off a single cable (single-channel), only one drive can talk at a time. With a two separate cables on a dual-channel, assuming a 2x drive RAID setup, then each of the drives potentially has full saturation available from the controller (discounting other limitations such as bus speed, etc.). Correct?

Does my G4 Gigabit, with it 33mhz PCI bus, even have a chance of needing a dual-channel setup considering that low bus speed?

Considering that, would it benefit from the UL3D card (let alone a ULD4)?

And looking over eBay, UL3D cards look to be PCI-X. Can PCI-X cards be used in my G4 Gigabit with basic, boring PCI slots?

There is no hardware Raid solution for OS 9.

All software solutions
SoftRaid utility for OS9
Express Stripe ATTO for OS9 and OS-X
Apple Raid Utility for OS-X

My setups
ATTO UL4D in OS-X (Tiger|Leopard) 4 HDD in two channels (Raid-0) Apple Raid Utility (speed up to 190 Mb/s)—Realizes the full potential of the 64bit PCI Bus

ATTO UL3D in OS9 2 HDD one channel (Raid-0) ATTO Express Stripe (speed up to 90mb/s)


Important, you will never be able to boot into OS9 from a software raid.

Offline aroneox

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #6 on: November 24, 2022, 01:23:33 PM »
Thanks for the clarification regarding OS 9 RAID booting. It makes sense as to why.

If there’s no hardware RAID on the OS 9 side, I think I’ll just stick with the single SCSI Atlas.

For your setup, are you using a dedicated OS 9 boot and application drive for your production software, and then using your RAID array as a dedicated “tape” for recording with the lowest latency possible?

Offline ivanshpak

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #7 on: November 24, 2022, 02:11:36 PM »
Thanks for the clarification regarding OS 9 RAID booting. It makes sense as to why.

If there’s no hardware RAID on the OS 9 side, I think I’ll just stick with the single SCSI Atlas.

For your setup, are you using a dedicated OS 9 boot and application drive for your production software, and then using your RAID array as a dedicated “tape” for recording with the lowest latency possible?

In Pro Tools, I use one external HDD (Glyph, with Seagate Cheetah 15k) to record audio

The internal RAID-0 back-up copies of the retrospect, and the library of audio samples and other audio archive

In the end, I realized that Pro Tools works more stable with one SCSI HDD

I also want to say that SCSI are fast HDD, it is very difficult to separate SSD from a 15k SCSI HDD of the latest generations in real operation, even with a decrease in speed to Ultra160

Of course, in synthetic tests, SATA SSD is faster, but in real life everything is much more interesting.

SCSI is not a panacea and I do not persuade anyone to use it, I just bought a huge amount of these HDD in my time and just use them for their intended purpose

Offline xerograph

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #8 on: April 09, 2023, 10:11:09 AM »
Important, you will never be able to boot into OS9 from a software raid.

I think this applys only for SCSI RAID on OS9 - right? Because I use several G4 Macs which all use different software and hardware RAID 1 solutions based on sATA and pATA cards as a OS9 only boot volume.

Offline ivanshpak

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Re: Is PCI card based hosted SCSI RAID a thing for MacOS?
« Reply #9 on: April 09, 2023, 02:16:39 PM »
Important, you will never be able to boot into OS9 from a software raid.

I think this applys only for SCSI RAID on OS9 - right? Because I use several G4 Macs which all use different software and hardware RAID 1 solutions based on sATA and pATA cards as a OS9 only boot volume.

Yes